The body of the camel will be painted dark brown.
The cowling area aluminum. All Tamiya acrylics.
The cockpit area faux wood. painted in a tan acrylic, when dry, streaked with brown artists oils.

Should the Oils be applied to the model first ...or last?
How thin should the oil paints be thinned?

Thanks for your advice.

I'm not certain what you're asking about applying the oils first or last. When you're doing wood grain you apply the oils after the base coat is dry. This may not necessarily be the last painting you'll do on your model.

Thinning shouldn't really be done at all; you want the pigment fairly thick so that you can drag the brush through it to create the wood grain effect. When I do mine I use the paint straight out of the tube. You'll find that you need very little to achieve a good effect. Remember that oil paint takes several days to dry completely. If you start handling your model too soon you can rub the paint completely off and then you'll have to do it all over again.

Should "wood" portion of the plane be painted first,
then the aluminum and brown?
Or, paint aluminum and brown first and then the "wood".
Can oil paint be masked using tape?

Ah, I see what you're getting at. Once it's dry it can be masked over but why take the chance? I'd do the aluminium and brown first and save the wood grain for last.